In conventional compact portable electronic apparatuses, the secondary battery (or a primary battery) is often used as a power source for reducing both the size and weight.
A power source such as a secondary battery generally has a high internal resistance. Unless some measures are taken, therefore, the compact portable electronic apparatuses having this type of power source are liable to develop a malfunction or become inoperative due to the voltage drop across the high internal resistance of the power supply when the power supply voltage is lowered. Such compact portable electronic apparatuses are inconvenient to handle for the user.
In order to prevent the malfunction, these compact portable electronic apparatuses have been configured in such a manner that the system data is initialized or the user is urged to perform the charging operation in the case where the source voltage drops below a predetermined threshold level. The source voltage of the compact portable electronic apparatuses undergoes a small change in various processes.
Assuming that the threshold voltage is constant, therefore, depending on the operating conditions, the source voltage is reduced below the threshold level temporarily and the system data are initialized without the knowledge of the user or the screen display for urging the initialization or charging is repeated often to the inconvenience of the user.